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991.
Hong Ping HE Yue Mao SHEN Guo Ying ZUO Wei Ming ZHU Xiao Sheng YANG Xiao Jiang HAO 《中国化学快报》2000,11(6)
Cla!tsenaexcavataBurm.f(Rutaceae)isabushwidelydistributedinYunnan,China.Leavesandbarksofthisplanthavebeenusedasfolkrnedicineforthetreatmentofdysentery,enteritis,andurethrainfection1.ClalISenaspeciesareknowntobetherichsourcesofcarbazolealkaloidsandcoumarins=-j.TheconstituentsofCexcavalacollectedinXishuangbannahavebeenstudied'andthispaperdescribestheisolationandstructureelucidationoftwonewO-terpenoidalcoumarins,excavacoumarinA(2)andexcavacoumarinB(3),andthel3CNMRspectraldataassignmentsfora… 相似文献
992.
Jian Ping LI* Qian Fu LUO Yi Yang SHEN Yu Lu WANG Hong WANG College of Chemistry Environmental Science Henan Normal University Xinxiang Department of Chemistry Luoyang Teacher''''s College Luoyang 《中国化学快报》2001,(2)
The subject of organic solid-state synthesis is a fascinating one. It has many advantages such as high efficiency and selectivity, easy separation and purification, mild reaction conditions, and environmental acceptability1. In recent years, this method has been widely used in a variety of organic reactions including substitution2, condensation3, oxidation-reduction4, rearrangement5 and elimination6. However, the solid state reaction using K3Fe(CN)6/KOH to oxidize substituted semicarbazides… 相似文献
993.
对ISO/IEC17025-1999和ISO/IEC指南25-1990进行了比较,分析了ISO/IEC17025-1999的显著变化,提出了由ISO/IEC指南25-1990质量体系向ISO/IEC17025-1999质量体系过渡的措施。 相似文献
994.
宏观热现象是由宏观物体中大量微观粒子(原子、分子…等)相互作用产生的无规则混乱运动引起的.分子体系的温度愈高、体积愈大,它的混乱运动程度就愈大,我们引入一个物理量S来表征这种运动的混乱度. 我们可以看出,混乱度S是温度T和体积V的函数S(T,V),或为能量E和体积V的函数S(E,V).我们在本文中证明,在缓慢的可逆热运动过度中,通过作微观的功和宏观功的方法,给体系一无穷小的能量dE,使其混乱度与体积的变化分别为dS与dV,则三者有如下关系:dE=TdS-pdV.这就是在可逆过程中的热运动基本方程,也就是传统热力学中所称的热力学基本方程. 相似文献
995.
Yong‐Qin Wei Ke‐Chen Wu Bo‐Tao Zhuang Zhang‐Feng Zhou Ming‐Xin Zhang Cai‐Ping Liu 《无机化学与普通化学杂志》2005,631(8):1532-1535
The silver complex Ag(PPh3)2(H2TMT) ( 1 )(H3TMT = 2,4,6‐trimercapto‐1,3,5‐triazine) has been synthesized and characterized. The ligand trimercaptotriazine exhibits a novel coordination mode and the complex shows a special hydrogen bonding linkage in the crystal packing. The colorless crystals of 1 exhibit broad emission in the visible region at room temperature. TDDFT calculation indicated that the π–π attraction is crucial for fluorescence of the title complex. 相似文献
996.
Ionic liquid 1-hexadecyl-3-methylimidazolium bromide [C16mim]Br was synthesized by solvent-free alkylation of N-methylimidzole with hexadecyl bromide. A large transparent single crystal of 1-hexadecyl-3-methylimidazolium bromide monohydrate ([C16mim]Br·H2O), 4 mm in length, was firstly obtained in the water-trichloromethane-toluene growth system (Vwater'Vtrichloromethane'Vtoluene = 0.1:1:2). The crystal structure was determined by single-crystal X-ray diffraction method. It crystallizes in the triclinic system, space group P1, with a = 5.4962(15), b = 7.839(2), c = 27.279(8) A, α = 94.375, β = 91.500, γ = 101.999°, Z = 2, V = 1145.2(5) A3, C20H41BrN2O, Mr = 405.46, Dc = 1.176 Mg/m3, μ = 1.804 mm^-1, F(000) = 436, the final R = 0.0523 and wR = 0.1345. The 3D supramolecular structure is constructed through weak interactions between imidazolium cations, Br- anions and lattice water molecules. The long alkyl chain to the imidazolium ring and lattice water molecules play an important role in the self-assembly process. Moreover, it is proposed that [C16mim]Br in water has aggregation behavior and the possible self-assembled structure is the interdigitated pattern. Finally, thermal stability of [C16mim][Br]·H2O was also studied by DSC and TGA analysis. 相似文献
997.
Huming Ren Yanhuai Ding Yong Jiang Fu Xu Zhilin Long Ping Zhang 《Journal of Sol-Gel Science and Technology》2009,52(2):287-290
ZnO nanofibers were prepared from zinc acetate/polyvinyl alcohol (PVA) by electrospun method. The morphological features,
crystallinity, mechanical and optical properties of the ZnO nanofibers were studied. The results show the specific surface
area of the ZnO nanofibers was influenced by the electrospun conditions. The specific surface area reached 389.7 m2g−1 as the average diameter was 232 nm. The XRD date reveals the nanofibers consist of a single phase of well-crystallized ZnO
with hexagonal structure. The elastic modulus of a single ZnO nanofiber was also characterized by nano-scale three-point bending
test. 相似文献
998.
WANG Xian-Ping DONG Ping YANG Ming CAO Zhuo-Liang 《理论物理通讯》2008,50(9):640-642
We propose a scheme for generating multi-ion graph states using many trapped ions in thermal motion. Our generation scheme is insensitive to external state since the interaction between ions and laser fields does not involve the external degree of freedom. The scheme can be well realized within the current experimental technique. 相似文献
999.
Zhi Chao Wang Lai Jun Wang Ping Zhang Song Zhe Chen Jing Ming Xu Jing Chen 《中国化学快报》2009,20(1):102-105
Three kinds of Pt/alumina catalysts were prepared by impregnation-hydrogen reduction,impregnation-hydrazine reduction and electroless plating methods.Their differences in the structures,specific areas and particle sizes were characterized by XRD,BET and TEM,respectively.Furthermore,their catalytic activities for the hydrogen iodide(HI)decomposition were evaluated in a fixed bed reactor.The results show that the catalyst 5%Pt/Al_2O_3 prepared by the electroless plating has the optimum catalytic properties... 相似文献
1000.
Based on the consideration of Boolean dynamics, it has been hypothesized that cell types may correspond to alternative attractors of a gene regulatory network. Recent stochastic Boolean network analysis, however, raised the important question concerning the stability of such attractors. In this paper a detailed numerical analysis is performed within the framework of Langevin dynamics. While the present results confirm that the noise is indeed an important dynamical element, the cell type as represented by attractors can still be a viable hypothesis. It is found that the stability of an attractor depends on the strength of noise related to the distance of the system to the bifurcation point and it can be exponentially stable depending on biological parameters. 相似文献